Structural basis for the neutralization of hepatitis E virus by a cross-genotype antibody

Abstract

Hepatitis E virus (HEV), a non-enveloped, positive-sense, single-stranded RNA virus, is a major cause of enteric hepatitis. Classified into the family Hepeviridae, HEV comprises four genotypes (genotypes 1-4), which belong to a single serotype. We describe a monoclonal antibody (mAb), 8G12, which equally recognizes all four genotypes of HEV, with ~2.53-3.45 nM binding affinity. The mAb 8G12 has a protective, neutralizing capacity, which can significantly block virus infection in host cells. Animal studies with genotypes 1, 3 and 4 confirmed the cross-genotype neutralizing capacity of 8G12 and its effective prevention of hepatitis E disease. The complex crystal structures of 8G12 with the HEV E2s domain (the most protruded region of the virus capsid) of the abundant genotypes 1 and 4 were determined at 4.0 and 2.3 Å resolution, respectively. These structures revealed that 8G12 recognizes both genotypes through the epitopes in the E2s dimerization region. Structure-based mutagenesis and cell-model assays with virus-like particles identified several conserved residues (Glu549, Lys554 and Gly591) that are essential for 8G12 neutralization. Moreover, the epitope of 8G12 is identified as a key epitope involved in virus-host interactions. These findings will help develop a common strategy for the prevention of the most abundant form of HEV infection.

Dynamics of 8G12 competitive antibody in “prime-boost” vaccination of Hepatitis E vaccine

“…In this work, a well characterized mouse neutralizing monoclonal antibody 8G12, which was shown to efficiently block the binding of naturally acquired anti-HEV antibodies to Hecolin Ò antigen p239, 27 was applied to develop a competitive ELISA assay to detect 8G12-like antibodies in serum samples. With serial serum samples collected from participants enrolled in a HEV vaccine clinical trial, we could detect 8G12-like antibody in all participants vaccinated from Hecolin Ò and HEV vaccine (Changchun), through the titers at prime vaccination varied in each participant.…”

“…22,26 Among these mAbs developed by Zhang J and Gu Y. et.al, broad neutralizing mAbs 8H3, 8C11, 8G12 recognize the conserved residues in the E2s dimerization region on ORF2 and can protect macaque rhesus from HEV challenge. 23,27 Previous studies showed that 8G12 can significantly block the binding of HEV convalescent sera as well as Hecolin Ò vaccinated sera from human and macaques rhesus to HEV ORF2 protein. 27 The rare predominant existence of 8G12 competitive antibodies (8G12-like antibodies) in serum indicated that most neutralizing antibodies elicited by HEV natural infection or Hecolin Ò vaccination might recognize similar epitope as 8G12 or epitopes in the vicinity.…”

“…23,27 Previous studies showed that 8G12 can significantly block the binding of HEV convalescent sera as well as Hecolin Ò vaccinated sera from human and macaques rhesus to HEV ORF2 protein. 27 The rare predominant existence of 8G12 competitive antibodies (8G12-like antibodies) in serum indicated that most neutralizing antibodies elicited by HEV natural infection or Hecolin Ò vaccination might recognize similar epitope as 8G12 or epitopes in the vicinity. These findings led to a very intriguing question that whether 8G12-like antibody played a prominent protective role in people vaccinated with Hecolin Ò .…”

Establishment of a Competitive Binding Assay Identifying the Different Characteristics of Neutralizing Epitopes of Hepatitis E Virus

“…The reduction of hepatitis E morbidity and mortality depended on vaccine prevention and effective diagnosis. Knowledge of epitopes of HEV was essential for vaccine preparation and diagnostic development [22]. The detection of specific antibodies in serum is one of the main diagnostic methods, and there is a growing number of serological assays for antibody detection.…”

“…Therefore, pORF 2 containing most immunogenic sites has been widely used for HEV immunological study, with a conformation-dependent character [25]. The structural basis of an immunogen to elicit neutralizing and protective antibodies is the neutralizing epitope, which is the main target of hepatitis E vaccine development [22]. We have previously reported that the p166 protein, a truncated protein of pORF 2 , can model HEV neutralizating epitope(s), and antibodies raised against p166 could cross-neutralize different genotypes of HEV [26].…”